Axial flow fan blade with noise reduction vent

Abstract

The invention aims to provide a kind of axial flow fan blade with noise reduction vent, including blade top, blade root, leading edge, trailing edge, pressure surface, suction surface, a space below blade top is provided with A type main stem air inlet hole, C type air outlet hole is set in the space and penetrates to pressure surface, C type air outlet hole is communicated with A type main stem air inlet hole, B type branch air inlet hole is opened on leading edge, B type branch air inlet hole extends to the space of A type main stem air inlet hole with arc shape and is communicated with A type main stem air inlet hole.The gas of the present application flows into air inlet hole from leading edge position, then is sprayed from pressure surface.This part of gas sprayed from pressure surface will have greater kinetic energy, when the air flow of blade pressure surface flows to blade suction surface due to pressure difference, it will be sprayed air flow and flow to blade trailing edge, and will not flow to blade top gap.Such will greatly inhibit the formation of blade top gap leakage vortex, thereby greatly weakening the aerodynamic noise of fan.

Description

Technical Field

[0001] The present invention relates to a blade, specifically an axial flow fan blade. Background Technology

[0002] Noise pollution, along with air and water pollution, is listed as one of the three major sources of pollution in the world today, and is one of the main factors that harm the environment due to industrial civilization. In order to control noise pollution and improve people's living and working environment, countries around the world have invested a lot of human and material resources in research on vibration reduction and noise reduction, and have formulated a series of standards and regulations.

[0003] Fans are widely used mechanical equipment in industrial and agricultural production and people's daily lives, covering multiple engineering fields such as power, electricity, chemical industry, metallurgy, and machinery. In recent years, the number of fans in use has been increasing year by year, the speed has been getting higher and higher, and the noise from fan operation has been having a more and more serious impact on people's lives.

[0004] For axial flow fans, aerodynamic noise is the primary noise source, while mechanical noise is much lower. The aerodynamic noise of a fan consists of broadband noise distributed across the frequency spectrum and discrete noise of various harmonics. The former is turbulent noise, caused by pressure and velocity fluctuations; the latter is rotational noise, caused by the interference between the fan's moving and stationary blades.

[0005] Theory and experiments show that when viscous fluid flows through a blade, various complex vortex systems are generated on and near the blade surface. Among these, tip leakage vortices and trailing edge shedding vortices generate significant aerodynamic noise. Current noise reduction methods for tip leakage vortices and trailing edge shedding vortices mainly involve adding a blade crown to suppress tip clearance leakage vortices and using a serrated trailing edge to break up large-scale trailing edge shedding vortices. Summary of the Invention

[0006] The purpose of this invention is to provide an axial fan blade with noise-reducing vents that can greatly suppress the formation of leakage vortices in the tip clearance, thereby significantly reducing the aerodynamic noise of the fan.

[0007] The objective of this invention is achieved as follows:

[0008] The present invention discloses an axial flow fan blade with noise reduction ventilation holes, characterized in that: it includes a blade tip, blade root, leading edge, trailing edge, pressure surface, and suction surface; an A-type main air inlet is provided in a space below the blade tip; a C-type air outlet is provided in this space, extending through to the pressure surface and communicating with the A-type main air inlet; a B-type branch air inlet is provided on the leading edge, extending in an arc shape to the space where the A-type main air inlet is located and communicating with the A-type main air inlet.

[0009] The present invention may also include:

[0010] 1. The length of the blade height is h, the chord length of the blade is b, the axis A1 of the type A main air inlet and the axis C1 of the type C outlet are both located in a plane parallel to the blade tip, the distance between this plane and the blade tip is h / 20, the axis of type A1 coincides with the middle arc of the blade, and the axis of type A1 is 4b / 5.

[0011] 2. The angle between the C1 type axis and the chord of the blade is 30°. The distance L between two adjacent C1 type axes is 6%-7% of the chord length b. The distance between the first C1 type axis and the intersection point 15 of the leading edge is b / 5, and the distance between the last C1 type axis and the intersection point 16 of the trailing edge is b / 6.

[0012] 3. The distance between the air inlets of adjacent B-type branches is h / 10, and the distance between the air inlet of the lowest B-type branch and the leaf root is not less than h / 2.

[0013] 4. The diameter of the air inlet of type A main trunk and type B branch air inlet can both be taken as 1 / 30 of the leaf height h, and the diameter of type C air outlet can be taken as 1 / 60 of the leaf height h.

[0014] 5. Establish a Cartesian coordinate system in the plane containing the C-type vent axis, with the intersection point of the front edges as the origin O, and the chord as the X-axis. Define the straight line passing through the origin O and perpendicular to the X-axis within the plane containing the C1-type axis as the Y-axis. Then, the A1-type axis can be represented by the following equation:

[0015]

[0016] In the above formula, b is the chord length, and d is the distance between the midpoint of the middle arc and the chord;

[0017] The C1 type axis can be represented by the following equation:

[0018]

[0019] In the above formula, i represents the i-th C1-type axis from the intersection point of the leading edge, b is the chord length, and L is the distance between two adjacent C1-type axes.

[0020] 6. Set the point located on the straight line connecting the intersection of the leading edge of the blade tip and the intersection of the leading edge of the blade root, and at a distance of h / 20 from the blade tip, as the origin O. Set the straight line passing through the origin O and parallel to the blade tip chord as the X-axis. Set the straight line connecting the intersection of the leading edge of the blade tip and the intersection of the leading edge of the blade root as the Y-axis. Set the straight line passing through the origin O and perpendicular to the projection plane as the Z-axis. The positive direction of the Z-axis points towards the suction surface.

[0021] The projection line B2 of the air inlet axis of type B branch can be represented by the following equation:

[0022]

[0023] The mid-surface F1 can be represented by the following equation:

[0024]

[0025] The axis of the air inlet of type B branch can be represented by the following equation:

[0026]

[0027] In the above formula, i represents the distance from the axis of the i-th B-type branch air inlet at the leaf tip, b represents the chord length, h represents the leaf height, and d represents the distance between the midpoint of the middle arc and the chord.

[0028] The advantage of this invention is that, for certain types of axial flow fans, the vortex noise generated by leakage vortices in the blade tip clearance has a major impact on the overall aerodynamic noise of the fan. Leakage vortices in the blade tip clearance occur because, during blade operation, the static pressure on the pressure surface of the blade is greater than the static pressure on the suction surface. Due to centrifugal force, gas on the pressure surface flows towards the suction surface of the blade through the gap between the blade tip and the casing. During this flow towards the suction surface, vortices form at the blade tip clearance, and relatively strong leakage vortices are formed near the blade tip on the suction surface, resulting in significant vortex noise. The feature of this invention is the provision of a series of air inlet channels at the leading edge of the blade and a series of air outlet channels on the pressure surface near the blade tip. This allows gas to flow into the inlet holes from the leading edge and then exit from the pressure surface. The gas exiting from the pressure surface possesses significant kinetic energy. When the airflow on the pressure surface flows towards the suction surface due to the pressure difference, it is carried by the exiting airflow towards the blade trailing edge, rather than flowing towards the blade tip clearance. This will greatly suppress the formation of leakage vortices in the blade tip gap, thereby significantly reducing the aerodynamic noise of the fan. Attached Figure Description

[0029] Figure 1 A cloud map showing the calculation results for an axial flow fan;

[0030] Figure 2 This is a schematic diagram of the overall structure of an axial flow fan;

[0031] Figure 3 This is a schematic diagram of the structure of the present invention;

[0032] Figure 4 A schematic diagram of the airfoil in the plane containing the axis of the C-type exhaust port;

[0033] Figure 5 This is a schematic diagram showing the distribution of the air intake vents on the leading edge.

[0034] Figure 6 This is a schematic diagram of the axis projection of the type B vent. Detailed Implementation

[0035] The invention will now be described in more detail with reference to the accompanying drawings:

[0036] Combination Figure 1-6 This invention relates to an axial flow fan blade with noise-reducing ventilation holes. For example... Figure 2 As shown, the overall structure of the present invention includes a fan housing 1, blades 2, a hub 3, blade tip clearance 4, and noise-reducing ventilation holes 5. Figure 3 and Figure 4 As shown, the blade includes a leaf tip (8), leaf root (9), leading edge (6), trailing edge (7), pressure surface (10), suction surface (11), type A main trunk air inlet, type B branch air inlet, and type C air outlet. Combined with... Figures 2-4 As blade 2 rotates with hub 3, due to the work done by blade 2, the static pressure on the pressure surface 10 of the blade is greater than the static pressure on the suction surface 11. Furthermore, the gas exhibits centrifugal force during rotation. Therefore, under the influence of the static pressure difference and centrifugal force, the gas flows from the pressure surface 10 through the blade tip gap to the suction surface 10, forming vortices at the blade tip gap 4, thus generating considerable vortex noise. Figure 1 The eddy current cloud map shows that the shedding vortex begins approximately 6 b / 5 from the leading edge and ends approximately 7 b / 6 from the trailing edge. Figure 1 As shown in the hydrostatic pressure cloud diagram, the hydrostatic pressure at the leading edge 6 of the blade is greater than the hydrostatic pressure at the pressure surface 10. Therefore, the idea of ​​reducing noise by opening vents that allow air to enter from the leading edge 6 and exit from the pressure surface 10 is feasible. Figure 3 As shown, the feature of this invention is that an A-type main air inlet is opened near the blade tip, followed by a series of B-type branch air inlets to increase the air intake, and then a series of C-type air outlets extending to the pressure surface 10. When the airflow flows from the pressure surface 10 through the blade tip gap 4 to the suction surface 11 under the action of the pressure difference, the gas ejected from the C-type air outlets will carry this part of the airflow towards the blade trailing edge 7. This can greatly limit the formation of leakage vortices in the blade tip gap 4, thereby greatly reducing the aerodynamic noise of the axial flow fan.

[0037] like Figure 4 As shown, the blade shape includes the mid-arc line 12, the intersection point of the mid-arc line and the leading edge of the blade shape 15, the intersection point of the mid-arc line and the trailing edge of the blade shape 16, and the chord 13. The mid-arc line is the line connecting the centers of the inscribed circles of the blade shape, and is simply called the midline. The chord is the straight line connecting the intersection points of the leading and trailing edges; the length of the chord is called the chord length, denoted by the letter b. The curved surface that runs through the mid-arc line at the blade tip and the mid-arc line at the blade root is called the mid-curve surface. Figure 3 In this context, F1 represents the mid-curved surface.

[0038] Depend on Figure 4 It can be seen that the axis A1 of the type A main intake port and the axis C1 of the type C outlet port are both located in a plane parallel to the blade tip, and are... Figure 5It can be seen that the distance between the plane and the blade tip is h / 20. The A1 type axis coincides with the mid-arc line, and the chord length corresponding to the A1 type axis is 4b / 5. The angle between the C1 type axis and the chord is 30°, and the distance L between two adjacent C1 type axes can be taken as 6%-7% of the chord length b. The distance between the first C1 type axis and the intersection point 15 of the leading edge is b / 5, and the distance between the last C1 type axis and the intersection point 16 of the trailing edge is b / 6.

[0039] The diameter of the C-type air outlet can be taken as 1 / 60 of the leaf height h; the diameter of the A-type trunk air inlet and the B-type branch air inlet can both be taken as 1 / 30 of the leaf height h.

[0040] Figure 5 The diagram shows the distribution of air inlets on the leading edge of the blade. As can be seen from the diagram, the A-type main air inlet on the leading edge is h / 20 from the blade tip, and the distance between adjacent air inlets is h / 10. In order to reduce the impact of the air vents on the fan performance, the air inlets are only distributed in the upper half of the leading edge, that is, the distance between the last air inlet and the blade root is h / 2.

[0041] To more accurately describe the position and shape of the Type A main air inlet and Type C air outlet, a Cartesian coordinate system is established on the plane containing the axis of the Type C air outlet. For example... Figure 4 As shown, the intersection point 15 of the front edges is taken as the origin O; the chord is taken as the X-axis; and the straight line passing through the origin O and perpendicular to the X-axis in the plane containing the C1-type axis is taken as the Y-axis.

[0042] The A1 type axis can then be represented by the following equation:

[0043]

[0044] In the above formula, b is the chord length, and d is the distance between the midpoint of the arc and the chord.

[0045] The C1 type axis can be represented by the following equation:

[0046]

[0047] In the above formula, i represents the i-th C1-type axis at the distance from the intersection point of the leading edges, such as... Figure 4 As shown, b is the chord length, and L is the distance between two adjacent C1-type axes.

[0048] To more accurately describe the location and shape of the air inlets on type B branches, such as Figure 6As shown, a spatial rectangular coordinate system is established on the projection plane. Let the blade tip chord be line 13.1, the blade root chord be line 13.2, and the line connecting the intersection of the blade tip leading edge and the blade root leading edge be line 14. The projection plane is composed of lines 13.1, 13.2, and 14. B2 is the projection of the axis of the B-type branch air inlet onto the projection plane. The point located on line 14 and at a distance of h / 20 from the blade tip is set as the origin O; the line passing through the origin O and parallel to the blade tip chord 13.1 is set as the X-axis; line 14 is set as the Y-axis; and the line passing through the origin O and perpendicular to the projection plane is set as the Z-axis, with the positive direction of the Z-axis pointing towards the suction surface.

[0049] The projection line B2 of the air inlet axis of type B branch can be represented by the following equation:

[0050]

[0051] On the other hand, the mid-curved surface F1 can be represented by the following equation:

[0052]

[0053] The axis of the air inlet of type B branch can be represented by the following equation:

[0054]

[0055] In the above formula, i represents the distance from the axis of the i-th B-type branch air inlet at the leaf tip, b represents the chord length, h represents the leaf height, and d represents the distance between the midpoint of the middle arc and the chord.

Claims

1. An axial flow fan blade with noise-reducing vents, characterized in that: Including leaves The leaf has a top, leaf root, leading edge, trailing edge, pressure surface, and suction surface. A main air intake hole is set in a space below the leaf top. An air outlet hole is set in this space, which extends to the pressure surface and is connected to the main air intake hole. A branch air intake hole is opened on the leading edge. The branch air intake hole extends in an arc shape to the space where the main air intake hole is located and is connected to the main air intake hole. The length of the blade height is h, the chord length of the blade is b, the axis of the main air intake and the axis of the air outlet are both located in a plane parallel to the blade tip, the distance between this plane and the blade tip is h / 20, the axis of the main air intake coincides with the middle arc of the blade, and the axis of the main air intake is 4b / 5.

2. The axial flow fan blade with noise-reducing vents according to claim 1, characterized in that: The angle between the axis of the air outlet and the chord of the blade is 30°. The distance L between the axes of two adjacent air outlets is 6%-7% of the chord length b. The distance between the axis of the first air outlet and the intersection point 15 of the leading edge is b / 5, and the distance between the axis of the last air outlet and the intersection point 16 of the trailing edge is b / 6.

3. The axial flow fan blade with noise-reducing vents according to claim 1, characterized in that: The distance between the air inlets of adjacent branches is h / 10, and the distance between the air inlet of the lowest branch and the leaf root is not less than h / 2.

4. An axial flow fan blade with noise-reducing vents according to claim 1, characterized in that: The diameter of the air inlet on the main trunk and the air inlet on the branches is 1 / 30 of the leaf height h, and the diameter of the air outlet is 1 / 60 of the leaf height h.

5. An axial flow fan blade with noise-reducing vents according to claim 1, characterized in that: Establish a Cartesian coordinate system in the plane containing the axis of the air outlet, with the intersection of the front edges as the origin O, and the chord as the X-axis. Then, define the straight line passing through the origin O and perpendicular to the X-axis in the plane containing the axis of the air outlet as the Y-axis. The axis of the main air inlet is then represented by the following equation: In the above formula, b is the chord length, and d is the distance between the midpoint of the middle arc and the chord; The axis of the vent is represented by the following equation: In the above formula, i represents the axis of the i-th air outlet from the intersection point of the leading edge, b is the chord length, and L is the distance between the axes of two adjacent air outlets.

6. An axial flow fan blade with noise-reducing vents according to claim 1, characterized in that: The point located on the straight line connecting the intersection of the leading edge of the blade tip and the intersection of the leading edge of the blade root, and at a distance of h / 20 from the blade tip, is set as the origin O. The straight line passing through the origin O and parallel to the blade tip chord is set as the X-axis. The straight line connecting the intersection of the leading edge of the blade tip and the intersection of the leading edge of the blade root is set as the Y-axis. The straight line passing through the origin O and perpendicular to the projection plane is set as the Z-axis. The positive direction of the Z-axis points towards the suction surface. The projection line of the branch air inlet axis is represented by the following equation: The mid-curved surface is represented by the following equation: The axis of the air inlet of the branch is represented by the following equation: In the above formula, i represents the distance from the axis of the i-th branch air inlet at the leaf tip, b represents the chord length, h represents the leaf height, and d represents the distance between the midpoint of the middle arc and the chord.

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